1. Technical Field
The present invention relates to a light guiding device and the like which guides video image light in order to present a video image formed by an image display element and the like to a viewer, and particularly to a virtual image display apparatus which is preferably applied to a head mount display designed to be mounted on the head of the viewer.
2. Related Art
Various optical systems to be embedded in a virtual image display apparatus such as a head mount display (hereinafter, also referred to as an HMD) designed to be mounted on the head of a viewer have been proposed (see JP-A-2013-200553, for example).
For the purpose of downsizing the optical system in such a virtual image display apparatus and separating a video image display apparatus from eye positions of the viewer so as not to interrupt eyesight thereof, it is preferable to use a relay optical system which forms an intermediate image after forming an image once with display image light in the optical system and shows the intermediate image in an enlarged manner.
However, in the case where the intermediate image is formed by using the relay optical system in an optical member such as a prism and there is dirt or contamination on the surface of the optical member near the intermediate image, the dirt or the contamination is viewed by the viewer in an enlarged manner. Therefore, it is desirable that the intermediate image be formed inside the optical member. However, it is difficult to form all the intermediate images inside the optical members in terms of optical design, and there is a possibility that a part of the intermediate images is inevitably formed on the surface of the optical member. In such a case, there is a possibility that dirt, contamination, or the like adheres on the surface of the optical member and causes image degradation.